Gas-fired heating device having a thermopile

ABSTRACT

A gas-fired heating device having a burner, a pilot to provide a pilot flame, a thermopile thermally coupled to the pilot flame and configured to generate a power in response to the pilot flame, an electrically controlled gas valve to control the flow of gas to at least one of the pilot and the burner, and a controller electrically coupled to the thermopile and the gas valve. The controller receives and is powered by the power from the thermopile. The controller initiates closing of the gas valve after a monitored component of the power, such as a voltage, traverses a threshold.

BACKGROUND

The present invention relates to heating devices, and particularly, togas heating devices. More particularly, the invention relates to acontroller used for controlling gas heating devices.

An exemplary gas-fired heating device is a gas water heater having aburner. Gas water heaters often include a combustion chamber and an airplenum disposed below a tank, such as a water tank. A gas manifold tube,an ignition source, a thermocouple, and a pilot tube typically extendinto the combustion chamber. When the temperature of the water in thetank falls below a set minimum, fuel is introduced into the combustionchamber through the gas manifold tube and a burner element. This fuel isignited by a pilot burner flame or the ignition source, and the flame ismaintained around the burner element. Air is drawn into the plenum viaan air inlet, and mixes with the fuel to support combustion within thecombustion chamber. The products of combustion typically flow through aflue or heat exchange tube in the water tank to heat the water byconduction.

SUMMARY

In one embodiment, the invention provides a new gas water heater havinga burner, a pilot, a gas valve coupled to the pilot, a thermopilethermally coupled to the pilot flame and operable to generate an outputvoltage, and a controller powered by the thermopile and coupled to thegas valve.

In a more specific embodiment, the controller is operable to control thegas valve based on the output voltage it receives from the thermopile.The controller includes a processor that processes a voltage valuereceived by the controller and communicates a shutdown signal forpreventing gas flow to the pilot and/or burner when an insufficientamount of voltage is outputted by the thermopile.

In another embodiment, the invention provides a controller for a gaswater heater. The gas water heater includes a burner, a pilot, anigniter, an electrically controlled gas valve, and a thermopile. Thethermopile can be positioned in a standing pilot flame provided by thepilot. The standing pilot flame causes the thermopile to generate anoutput voltage that it used to power the controller and the electricallycontrolled gas valve. The controller responds to an insufficient amountof output voltage provided by the thermopile by, for example, closingthe electrically controlled gas valve. The insufficient amount of outputvoltage can indicate the presence of a possible flammable vapor event ora possible lint, dust, or oil blockage event. Once the electricallycontrolled gas valve receives the shutdown signal it closes and preventsgas flow to the pilot and burner.

In another embodiment, the invention provides a method of controlling agas water heater. The gas water heater includes a burner, a pilot, anigniter, a thermopile, a controller, and a gas valve. The method caninclude detecting a possible flammable vapor event or a possible lint,dust, or oil blockage event. The thermopile produces an output voltagein response to a standing pilot flame generated by the pilot andigniter. The output voltage generated by the standing pilot flame can bebetween about 400 and 800 millivolts. When the thermopile outputs aninsufficient amount of voltage, a voltage less than 400 millivolts, forexample, the controller generates a shutdown signal and closes the gasvalve. Alternatively, when the thermopile outputs too much voltage, avoltage greater than 800 millivolts, for example, the controllergenerates the shutdown signal and closes the gas valve. The closing ofthe gas valve prevents gas flow to the pilot and burner, therebypreventing any combustion from occurring.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a gas water heater.

FIG. 2 is a sectional view of the bottom portion of the gas waterheater.

FIG. 3 is a block diagram of a portion of the gas water heater.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

FIGS. 1 and 2 illustrate a storage-type, gas-fired water heater 10 thatincludes a base pan 15. The base pan 15 may be constructed of stampedmetal or molded plastic, for example, and includes a generallyhorizontal bottom wall 20, a vertical rise 25 having an air inletopening 27, and an elevated step 30. The water heater 10 also includes awater tank 35, insulation 40 surrounding the tank 35, and an outerjacket 45 surrounding the insulation 40 and the water tank 35. A skirt50 is supported by the base pan's elevated step 30 and in turn supportsthe water tank 35. The elevated step 30 also supports the insulation 40and jacket 45.

In addition, the elevated step 30 supports a divider 60 that divides thespace between the bottom of the tank 35, skirt 50, and the base pan 15into a combustion chamber 65 (above the divider 60) and plenum 70 (belowthe divider 60).

A cold water inlet tube 75 and a hot water outlet tube 80 extend througha top wall of the water tank 35. A flue 85 extends through the tank 35,and water in the tank 35 surrounds the flue 85. The flue 85 includes aninlet end 90 and an outlet end 95.

The combustion chamber 65 and plenum 70 space are substantiallyair-tightly sealed, except for the air inlet opening 27 and inlet end 90of the flue 85. Seals 105 between the skirt 50 and the tank 35 and basepan 15 assist in sealing the space. The seals 105 may be, for exampleand without limitation, fiberglass material or a high-temperature caulkmaterial. A radiation shield 110 sits on the divider 60 within thesealed combustion chamber 65 and reflects radiant heat up toward thetank 35.

A flame arrester 115 is affixed in a sealed condition across an opening120 in the divider 60 such that all air flowing from the plenum 70 intothe combustion chamber 65 should flow through the flame arrester 115.The air inlet 27, air plenum 70, and opening 120 in the divider 60together define an air intake for the combustion chamber 65, and airflowing into the combustion chamber 65 through the opening (see arrowsin FIG. 2) 120 should flow through this air intake and the flamearrester 115. It should also be noted that the position and orientationof the flame arrester 115 are not limited to those shown in thedrawings, and that substantially any construction will work providedthat the flame arrester 115 acts as the gateway for the air flowing intothe combustion chamber 65 from the plenum 70. Sealing members 125 sealthe periphery of the flame arrester 115 to the divider 60 to reduce thelikelihood of air circumventing the flame arrester 115. In alternativeconstructions, a single sealing member 125 may be used to seal the flamearrester 115 with respect to the divider 60, or if the flame arresterfits snugly against the divider 60, no sealing members 125 may beneeded. The flame arrester 115 prevents flame within the combustionchamber 65 from igniting flammable vapors outside of the combustionchamber 65.

With reference again to FIG. 2, the air inlet 27 is covered by a lint,dust, and oil (“LDO”) filter 130 mounted to the outer surface of thebase pan 15. The LDO filter 130 filters air flowing into the plenum 70and reduces the likelihood that the flame arrester 115 will becomeoccluded by lint or other debris.

A burner 155 in the combustion chamber 65 burns a mixture of fuel andair to create the products of combustion that flow up through the flue85 to heat the water in the tank 35. The burner 155 receives fuelthrough a gas manifold 160 that extends in a sealed condition through anaccess door 165 mounted in a sealed condition over an access opening inthe skirt 50.

The construction shown (illustrated in FIGS. 1 and 2), employs anon-powered gas valve/thermostat assembly 170 mounted to the water tank10. As used herein, the term “non-powered” refers to a device that isnot powered from electrical mains. However, it is envisioned that theassembly 170 can be connected to electrical mains. A gas main 175provides fuel to the input side of the assembly 170. The assembly 170includes a controller 200 (FIG. 3) and a water temperature probe 180that is threaded into the tank side wall 35. Connected to the outputside of the assembly 170 are the gas manifold 160, a pilot burner 185, athermopile 190, and an igniter 195. The pilot burner 185, thermopile190, and igniter 195 extend into the combustion chamber 65 in a sealedcondition through a grommet in the access door 165.

The assembly 170 provides a flow of fuel to the pilot 185 to maintain astanding pilot burner flame, and this construction is thereforegenerally referred to as a “continuous pilot ignition” system. Theigniter 195 is used to initiate the flame on the pilot 185 withouthaving to reach into the combustion chamber with a match. A spark isgenerated by the igniter 195 in response to pushing a button on theassembly 170. The thermopile 190 provides feedback to the assembly 170and controller 200 as to the presence of flame at the pilot 185. Anexemplary thermopile 190 is a model Q313 thermopile generatormanufactured by Honeywell.

The assembly 170 permits fuel to flow to the burner 155 in response to awater temperature sensor (e.g., the water temperature probe 180)indicating that the water temperature in the water tank 35 has fallenbelow a selected temperature. When fuel flows to the burner 155, it ismixed with air and the mixture is ignited when it contacts the pilotburner flame. Once the water temperature sensor indicates that the waterhas reached the desired temperature, the assembly 170 shuts off fuelflow to the burner 155, and the water heater 10 is in “standby mode”until the water temperature again drops to the point where the assembly170 should again provide fuel to the burner 155.

An electrically controlled gas valve 205 (FIG. 3), or more specifically,an electronically controlled gas valve is biased in the closed positionwith respect to the gas manifold 160 and the pilot 185. The controller200 stores some energy in a storage device 200 that allows for the gasvalve 205 to be opened while igniting the pilot flame. The start uprequires a user to actuate the push button of the assembly 170 which inturn opens the gas valve 205 and triggers the igniter 195. The igniter195 provides a spark to the pilot 185 while gas is flowing andestablishes the pilot flame. The thermopile 190 is positioned near orwithin the pilot flame and produces an output voltage in response to thepilot flame. The output voltage is used as a power source by thecontroller 200, which keeps the electrically controlled gas valve 205open for the pilot flame 190. An exemplary electrically controlled gasvalve 205 that can be used with the invention is a model WV8840B gasvalve, manufactured by Honeywell. Before proceeding further, the gasvalve 205 is shown in FIG. 3 as a single device providing fuel to boththe burner 185 and the pilot 190. It should be understood, however, thatthe gas valve 205 can include multiple valves that are individuallycontrolled.

The assembly 170 is shown in FIG. 3 as including the controller 200. Thecontroller 200 receives a power from the thermopile 190, the powerhaving a plurality of components (e.g., a voltage, a current). In oneconstruction, the thermopile 190 provides a normal operation (ornominal) voltage of 400 to 800 millivolts to operate and control theassembly 170. The output voltage is recognized as being in aninsufficient output voltage (state) by the controller 200 if the outputvoltage is not within this range. For example, if the voltage is greaterthan 800 millivolts, then the pilot flame may be burning too hotindicating a first potential issue. Similarly, if the voltage is lessthan 400 millivolts, the pilot flame may be burning too cool indicatinga second potential issue.

In a more specific construction, the controller 200 issues a flag orsignal after the output voltage traverses a first threshold voltage(e.g., about 400 millivolts). The signal can be provided to an outputdevice (e.g., a light emitting diode, a display, an audible alarm, etc.)of the assembly 170. The controller 200 can close the gas valve 205,thereby deactivating the gas water heater 10, after the output voltageprovided by the thermopile 190 traverses a second threshold voltage(e.g., about 300 millivolts). The gas valve 205 closes in response to asignal (e.g., the application or removal of a voltage, an instruction,etc.) being sent from the controller 200 to the gas valve 205.

In the construction shown in FIG. 3, the controller 200 includes aprocessor 220 and memory 225. The processor 220 executes instructionsfrom the memory 225 to control the assembly 17, and consequently the gaswater heater 10. The memory can also store diagnostic and trending data,which can be helpful to diagnose a potential issue before it occurs andprovide more detailed information if a potential fault condition occurs.The controller 200 also includes signal conditioning circuitry 230 thatcan condition signals to and from the controller 200. For example, thetemperature sensor 185 can be conditioned to a voltage within arecognizable range for the processor 220. As discussed above, thecontroller 200 can include a storage device 210, such as a supercapacitor, that can provide additional or supplemental power whennecessary to operate the assembly 170. The assembly 170 also includes aninput/output interface 240 for an operator to interact with the gaswater heater 10. For example, an operator can interact with the assemblyto establish a set point temperature for the water heater 10, ignite thepilot flame 180, and similar function normally associated with a gaswater heater 10. Further, the assembly 170 can provide information tothe operator, including errors or faults determined by the controller200. It should also be understood that the controller 200, and morebroadly the assembly 170, can operate other elements of the water heater10 not shown. For example, the water heater 10 can include dampersand/or blowers to promote operation of the gas water heater 10.

Once the gas valve 205 closes due to a possible error condition, the gaswater heater 10 will not reignite until it is serviced by the user or aserviceperson. The user or serviceperson can read the diagnostics fromthe controller 200 and appropriately address the condition causing thepossible error condition.

As discussed above, the controller 200 can monitor a component (e.g.,voltage) of the power supplied by the thermopile 190. For example, thecontroller 200 can monitor the voltage to determine the status of thepilot flame. For example, the controller 200 can monitor the voltage todetermine whether the pilot flame indicates a normal flame burn (ornormal state) or an abnormal flame burn (or fault state). The faultstate can result from an improper burn by the pilot flame. Exampleevents that may cause an improper burn can include a possible lint,dust, or oil (LDO) filter blockage event, a possible flammable vaporevent, a possible improper ventilation event (e.g., the blower orexhaust system not properly discharging the exhaust), and a possibleoverheating event. For a specific example, a substantial blockage of theLDO filter results in an improper burn by the pilot flame, to which thevoltage value provided by the thermopile 190 is reduced. When thevoltage value traverses the threshold indicating a possible LDO filterblockage event, the controller 200 will take an action. The action maybe providing an error output with the user interface 240 or may beproviding a signal to the gas valve 205 to restrict gas to the burner155 and/or pilot 185. Other thresholds can be used to determine otherabnormal flame states. It is envisioned that the various thresholds canbe determined by empirical testing and that a single threshold may beused for one or more fault states. In one construction, a nominalvoltage range for the thermopile 190 is 400-800 millivolts, andconsequently a range for a threshold indicating abnormal operation isbetween about 275 and 450 millivolts, with a preferred range of 330 and400 millivolts. It is also envisioned that multiple thresholds can beused for a particular state—a first threshold for providing a warningand a second threshold for closing the gas valve 205.

Thus, the invention provides, among other things, a new and usefulgas-fired heating device having a thermopile. Various features andadvantages of the invention are set forth in the following claims.

1. A gas water heater comprising: a burner; a pilot to provide a pilotflame; a thermopile thermally coupled to the pilot flame and configuredto generate a power in response to the pilot flame; an electricallycontrolled gas valve to control the flow of gas to at least one of thepilot and the burner; a controller electrically coupled to thethermopile and the gas valve, the controller to receive and be poweredby the power from the thermopile, and to initiate closing of the gasvalve after a monitored component of the power traverses a threshold. 2.The gas water heater of claim 1 wherein the threshold indicates anabnormal flame state for the pilot flame.
 3. The gas water heater ofclaim 1 wherein the threshold indicates the detection of a possibleflammable vapor event.
 4. The gas water heater of claim 1 wherein thethreshold indicates the detection of a possible lint, dust, and oil(LDO) filter blockage event.
 5. The gas water heater of claim 1 whereinthe threshold indicates the gas water heater has a possible improperventilation event.
 6. The gas water heater of claim 1 wherein thethreshold indicates the gas water heater has a possible overheatingevent.
 7. The gas water heater of claim 1 wherein the controllerincludes a processor and memory.
 8. The gas water heater of claim 1wherein the power from the thermopile includes a voltage, and whereinthe monitored component includes the voltage.
 9. The gas water heater ofclaim 8 wherein the threshold for the monitored component is betweenabout 275 and 450 millivolts.
 10. The gas water heater of claim 1wherein the controller includes an electronic device and the gas valveincludes an electronically controlled gas valve.
 11. The gas waterheater of claim 10 wherein the power for opening the electronicallycontrolled gas valve originates from the power from the thermopile. 12.A safety system for use in a gas water heater including a burner, apilot, and a gas valve, the safety circuit comprising: a thermopile tobe thermally coupled to a pilot flame of the pilot and configured togenerate a power having a voltage in response to the pilot flamethermally interacting with the thermopile; a controller electricallycoupled to the thermopile and for connecting to the electronicallycontrolled gas valve, the controller to be powered by the power from thethermopile, to monitor the voltage to determine a pilot flame status,and to control the gas valve based on the pilot flame status.
 13. Thesafety system of claim 12 wherein the pilot flame status includes astatus indicating a normal flame burn.
 14. The safety system of claim 12wherein the pilot flame status includes a status indicating a possibleabnormal flame burn.
 15. The safety system of claim 14 wherein thecontroller initiates the closing of the gas valve after the pilot flameindicates the possible abnormal flame burn.
 16. The safety system ofclaim 14 wherein the controller determines a possible abnormal pilotflame burn when the voltage is between about 275 and 450 millivolts. 17.The safety system of claim 12 wherein the controller includes aprocessor and memory and wherein the memory includes diagnosticthresholds for indicating the possible abnormal flame burn.
 18. Thesafety system of claim 12 wherein the safety circuit further includesthe gas valve, and wherein the gas valve includes an electronicallycontrolled gas valve.
 19. The safety system of claim 18 wherein thepower for opening the electronically controlled gas valve originatesfrom the power from the thermopile.
 20. A method for controlling a gaswater heater including a burner, a pilot, a thermopile, a controller,and an electronically controlled gas valve, the method comprising:establishing a pilot flame with the pilot; powering the controller witha power generated by the thermopile thermally interacting with the pilotflame, the power having a voltage; monitoring the voltage with thecontroller; detecting a possible LDO filter blockage event or a possibleflammable vapor event with the monitored voltage; generating a shutdownsignal with the controller in response to detecting the possible LDOfilter blockage event or the possible flammable vapor event; and closingthe electronically controlled gas valve in response to the shutdownsignal.
 21. The method of claim 20 and further comprising opening theelectronically controlled gas valve with power originating from thethermopile.